Circuit protective device



@ma il@ wm MKM F. J. METZGER ET AL C IRCUIT PROTECTIVE DEVICE Filed Nov. l, 1922 BY A ' afm' ATToRNEx/y FLOYD il'. Nl i ZGER, OF NIEW' YORK, N. Y., AND JOHN T. OER, 0F ELIZ t.

WETH, NEW JEJE,-

SEY, ASSIGNORS TO AIR REDUCTION COMPANY, INCORPORATED, 01E NEW TOEN,

nr. r., a coona'rron or new Yoan.

crneurr rnornc'rrvn nnvrcn application led. November 1, 1922. Serial No. 598,305.

To all 'whom t may concern.:

Be it known that we, lFnorn `J. Mn'rzenn, a citizen of the United States, residing at New York cit in the county of New York, State of New ork, and JOHN T. ORB, a citizen of the United States, residing at Elizabeth, in the county of Union, State of New Jersey, have invented cert-ain new and useful Improvements in Circuit Protective Det@ vices; and We do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others 'skilled in the art to which it appertains to ineke and use the same.

rllhis invention relates to protective devices for electrical apparatus and circuits whereby stray currents at high potential may be excluded therefrom, the device ling particularly adapted for use as a llghtning arrester .although it is capable of diverting currents of much lower potential.

The device which is the subject matter of the present application vmay be utilized in connection with the various electrical circuits, particularly radio aerials, telephone and telegraph hues, railroad signal and other signal, lighting and power circuits.

The most common source of dangerin electrical circuits is lightning, and it is usual to employ protective devices whereby currents 'from this source are diverted to the ground and thus prevented from damaging instruments and machinery or endangering persons who are working with such apparatus. The introduction of power transmission at high potentials has added another source of danger since the high potential conductors sometimes come in contact with circuits which are not designed to receive currents of the character conveyed by power transmission lines.

'The devices heretofore employed todivert currents at high potential have been of various kinds but depend generally upon the use of a gap across which the high potential current may pass through air at varyinr pressures or through high resistance conductors suchV as granulated carbon. Such devices are not sensitive andhave a low current caacity. rlhey arey useful, moreover, only in against rela-tively low voltages such as are present in lighting and power lines.

The present invention depends upon the use .of gases of relatively high conductivity such as neon which, possessing a, relatively low dielectric strength, is easily broken down to permit the passage of currents at relatively low potentials and which, moreover, Vbecause of its conductivity, has a high current capacity, thus permitting the current from the source of high potential to pass readily to the ground where it is dispersed. The use of neon for this purpose hasbeen suggested heretofore but protective devices containing neon have not been available, probably because of the fact that such devices are readily disrupted owing to the heating e'ect of the current in passing therethrough. The electrodes employed in these devices have, moreover, been unsuited to the peculiar objects of the device, being of such a nature that they are readily destroyed by the current, particularl where the area exposed to the gas is insu cient to permit the proper discharge of the current through the gaseous atmosphere. llt has not been recognized, moreover, that the device should contain suHicient neon to provide the desired capacity, and the failure to appreciate this and other limitations has resulted in the failure of all attempts to utilize neon for the purpose described.

It is the object of the present invention to provide a device which overcomes the defects of high potential protectors as heretofore known and to provide a simple and e'ective means whereby high potential currents may be diverted from apparatus and machinery of an electrical character, the device having an effective life which reduces the maintenance cost and ensures the desired protection.

lin carrying out the invention the neon is disposed within a tube, preferabl of glass, having an external diameter of t ee-quar ters of an inch or thereabouts and being approximately two inches long. The size of the tube will vary Withthe desired ca.- pacity, 'the size stated being that best adapt ed for general purposes. The neon within the tube may be at any desired pressure, preferably between 5 and 50 mm., the preferred pressure being approximately 30 mm. of mercury.l The tube is provided with electrodes s aced apart and sealed throughy the walls, t e form of the electrodes being an important feature of the present invention as is hereinafter more fully set forth.

We have discovered that in order to maintain the effective life of the tubes employed as protective devices, it is necessary to distribute the heat which is generated by the passage of current therethrough. When a igh potential current passes through such a tube for even a short period, the electrodes and the gas within the tube become highly heated. Since the electrodes are of metal the heat is conducted rapidly to the walls of the tube where the electrodes are sealed" therethrough, and the uneven heating of the glass results in shattering the same, sometimes before the current has been fully diverted. This result, so far as it is caused by unequal expansion of the metal and the glass, may be avoided by the utilizationof suitable metal for the electrodes or lead-in conductors. Copper-clad conductors are preferred for this purpose. This precaution alone will not prevent shattering of the tubes. This may be avoided, however by providing two or more conductors leading to each electrode which are sealed through the glass wall at points spaced from each other. The heat is by this means delivered to the glass in a more uniform manner and the tube thus protected has a greatly increased life.

Another desirable feature of the present invention is the arrangement of the conductors in the form of loops which provide the desired electrode area. This structure permits the provision of the electrodes in their simplest form, avoiding the joining of different metals or the use of electrodes of larger size than the conductors secured to the ends thereof. In all such constructions it has been found that the electrodes become se arated from the conductors at the first dlscharge of current through the tube and the tubes are thereafter worthless. The loops employed in accordance with the invention may be variously arranged, being parallel to each other, for example, or disposed with their edges opposed.` Preferably in a tube of the size described, a conductor having a diameter of .025 inch is formed with the desired loops, and the ends are spaced apart and sealed through the Wall of the tube. IThis provides a rigid support for the electrode in addition to its heat-distributing function, and tubes so constructed will permit the passage of currents of twenty amperes or more repeatedly without destruction, a result which cannot be accomplished by `tubes such as have been known heretofore.

In the accompanying drawing the preferred forms of the invention are shown by way of illustration, it being understood that these forms are merely su gestive and that the primary features of t e invention may be utilized in various ways.

Fig. 1 is a side elevation of theinvention;

Fig. 2 isa plan view thereof;

Fig. 3 is a lplan view of an electrode of slightly modi ed form; and

Fig. 4 is an end elevation of one of the electrodes shown in Fig. 3.

Referring to the drawing, 5 indicates a tube Aof glass or other suitable materials which may be of the dimennsions hereinbefore stated or larger if the capacity of the tube is to be increased. It should be noted that a suicient gas capacity is essential to the continued life of the tubes, and the capacity provided should be ample to convey the currents which may pass through the tube. Two electrodes 6' are provided, the electrodes consisting of a looped conductor of suitable material as hereinbefore described. The ends of the coils are twisted at 7 to provide a rigid stem and the ends 8 are separated and sealed throu h the flattened ends of the tube. The en s 8 of the conductor distribute the heat from the electrodes and also serve as supports therefor so that the electrodes are quite rigidly held in proper relation within the tube.

ln Figs. 3 and 4 a slightly different form of electrode is illustrated, the only difference being in the arrangement of the loops 10 which are opposed in parallel relation.

The device described may be utilized in connection with electrical circuits in various ways. The conductors 8 at one end of the device should be connected to the ground in the usual manner jof making ground connections and the conductors at the opposite end of the device should be connected to the circuit which is to be protected. In the case of wireless installation the device is in a shunt connected to the aerial and to thel ground. The device may be in a similar manner connected to telegra h, telephone, railroad si a1 and other circuits.

The large capacity and the stability of the construction described ensures an extended life for the device. Current may ass repeatedly between the electrodes wit out endangering the glass tube or destroying the electrodes. The necessity of constantl replacing the device is thus avoided an the avoidance of constant inspection which would otherwise be necessary in the mainte nance of a circuit protected by safety devices is a considerable advantage, particularly where thousands of such evices are installed as in railroad signaling work.

While the invention has been described termal with particular referenceto tubes containing neon, it is to be understood that the device embodying the electrodes may contain gases other than neon. '.lhus the atmosphere of the device may be of rarelied cuits the combination of afrangible vessel and electrodes therein consisting of loops adapted to provide a relatively large surlace area, each electrode having two branched conductors sealed through the wall ot the vessel in spaced relation, the conductors bein twisted Within the vessel to provide a sti support for the electrodes.

2. .dn electrode comprising a looped conductor twisted adjacent the loop to provide a stid support therefor.

3.l An electrode comprising a loomd con.- ductor twisted adjacent the oop to provide a stiH support therefor and having tvvo or more branches adapted to .he sealedthrough the Wall of a receptacle.

d. ln a safety device `tor electrical circuits the combination of a vesl and electrodes therein, each consisting ol a plurality ol turns of wire forminga coil, the Wire be ing twisted behind the coils to provide a sti support therefor.

5. ln a safety device lor electrical circuits, the combination of a vessel and electrodes therein, each consisting of a plurality ol turns ol Wire forming a coil, the coils being disposed edge to edge with their ares in parallel relation.

ln testimony whereof We ax our sigriiorn J. Marrone. tout r. our. I

natures. 

